Collision of Indian Plate and Indus Tsangpo Suture Zone: Some Geological Constraints

Abstract

Abstract:The occurrence of Gondwana affinity Permo-Carboniferous glacial deposits in northern Tibet, Lhasa Block and Qiangtang Block obviously suggests that India continued into Tibet at that time. Significant also is that paleoclimatic continuity was maintained over landmass of India and Tibet from Paleozoic through the Cenozoic eras up to the Pleistocene. The age and origin of the Indus-Tsangpo Suture (ITS) is doubtful because the ophiolites are about 100 Ma older than the supposed collision. Similarly, the progressive under-thrusting of the Indian plate below the Tibetan plate is deemed unlikely, as the ophiolites must have formed an 8-20 km thick wall between the two plates and it was not possible for the Indian Plate to cross it. Probably the apparent northward migration of India indicates a northward migration of the North Pole. Similarly, there is no explanation for the fact that, if underthrusting has taken place, why did the Himalayan uplift occur some 500 km from the Indus-Tsangpo suture instead of being along the collision zone itself, negate under thrusting. The double thickness of the crust in Tibet is not a unique feature in that it continues south of the so-called Indus-Tsangpo suture, as also in the Pamir; it is of about the same order in the Andes. Whereas the Tibetan glacial indicate that India and Tibet were not separated in the Carboniferous, Lystrosaurus fauna suggests it for the Lower Triassic and the ophiolites for the Jurassic-Cretaceous. The development of rift valleys and normal faults cutting across the Indus-Tsangpo suture (ITS) shows that even in the Quaternary India and Tibet was together. Indeed, the measured Cambrian diameter is 50% of the Earth where as in Upper Permian it was about 55-60% with the North Pole near Verkhoyansk and the South Pole to the southeast of South Africa. Evidently the Earth is expanding and the rate of expansion has progressively accelerated through time is supported by decline in the gravitational constant from about one third to about one half of the present from Precambrian up to Mesozoic.